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Over the garden fence: Soil quality is key for better crops

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In The Gardening for Fun and Profit class this past week Nadine Davitt spoke about the manufacture of the Penn State Compost. She said it is used to improve soils around campus and is also for sale to the general public at Lions Surplus on campus.

Soil quality is the key ingredient in any vegetable garden, flowerbed or landscape planting. Soil provides the nutrients and water necessary for plant growth, and also protects fragile root systems from the elements.

Good water drainage is one indicator of quality soil. Even the most fertile soil will probably not produce a quality crop if it drains poorly. Poor drainage means that water has replaced the all-important air in the soil, smothering the roots. Some plants are more sensitive to lack of air than others — roses and yews, for example, are seriously damaged by wet soils. You have heard the expression “that a certain plant does not like wet feet.”

Adding organic matter is a very effective way to improve the quality of just about every soil. Organic matter will increase the pore space and drainage rate of heavy clay soils and in a sandy soil, which generally drains too quickly and holds too little water; organic matter will increase the water capacity of the soil.

Most garden soils do not have enough organic matter for good plant growth. The soil should have at least 3 to 5 percent organic content, and for many plants more than 10 percent would be better. Whenever the organic matter is added to a soil, it should be thoroughly worked in as deeply as possible to avoid creating layers of organic matter in the soil, which will create barriers to aeration, water movement and root penetration.

Organic matter also serves as a nutrient base for the bacteria and microorganisms that are so vital to the life of the soil. As these organisms break down organic matter, small amounts of plant nutrients are continually being released to the plant roots. The byproducts of organic matter breakdown also help hold the soil particle apart, which improves soil drainage and aeration.

Manure has been a traditional source of organic matter for the soil. However, finding a source and transporting it is difficult. Good aged or well-composted manure is still and excellent soil conditioner, and you can then add needed nutrients with a commercial fertilizer. You can purchase bag of dehydrated manure such as Bovung that is easily handled and applied. It has a fertilizer analysis of 1-1-1. Composted chicken manure is an excellent source of nitrogen, potassium and phosphorous. Fresh chicken manure is high in ammonia and can burn or kill plants. The composting process mellows out the nutrients and makes them more available to the plants.

Peat moss is also an effective source of organic material to incorporate into the soil if you are planting rhododendrons, blueberries or any other acid-tolerant plants.

Other organic materials that can be spaded into the garden soil are sawdust, straw, old hay, rotted leaves, peanut or buckwheat hulls, shredded bark and chopped corn stalks. If these materials are fresh and not composted or aged, soil bacteria breaking down the materials will have a high demand for soil nitrogen and plant quality may suffer. An initial application of about a quarter pound of nitrogen per each 100 square feet of soil area will be a start.

It is important to remember that soil organic matter is not a permanent part of the soil but is constantly being broken down so it must be continually added to the soil. It is a good idea to add about an inch of organic matter each time you work the soil each season. Such a practice will retain quality soil and constantly improve lesser-quality soils, however, incorporating large quantities of composted material at any one time may cause a temporary imbalance in the available nutrients in the soil.  

Bill Lamont is a professor and extension vegetable specialist in the department of plant science at Penn State and can be reached by email at wlamont@psu.edu.